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Glass & Glass Blowing

To make glass requires only sand (silicon dioxide), soda (sodium carbonate), lime (calcium oxide) and a lot of heat. It is

said that Roman seamen discovered glass while cooking on their open fires on beaches. All the ingredients of glass were present in and around their campfires. The sand provided the silicon and rocks around the fires were in some parts of the Mediterranean made of a mineral called Natron. This is a naturally occurring mixture of sodium carbonate (soda) and other carbonates. It is also found in dry saline lakebeds in arid climates. One such place where Natron occurred, also known to the Romans, was in Egypt. The heat of the fire caused the Natron to react with the sand and eventually they would be left with puddles of a liquid glass.

The first accurate record of glass manufacture was in Mesopotamia about 2250 years ago where potters fused sand and minerals together while firing their clay pots. Later the Phoenicians, particularly along what is now the Syro-Palestinian coast started blowing air down a metal tube with a blob of molten glass on the end. This resulted in the production of glass tubes and bubbles thus founding the art of glass blowing.

The first metal blowpipe therefore came into wide use in the 1st and 2nd century B.C. and glass production increased particularly in the Roman world. The Phoenicians became famous for their glassworks and glass-blowing techniques and eventually they moved their workshops from the eastern part of the Roman Empire to Italy itself. Rome eventually became a major glassblowing centre and subsequently other areas including Venice and Murano also established themselves. One of the most prolific glassblowing centres of the Roman world by the late first century was Cologne on the River Rhine in Germany.

From here the glassblowing art was carried to Europe and the Renaissance witnessed the revitalization of the glassblowing industry. Later the technique of glassblowing coupled with the cylinder and crown methods was used to manufacture sheets of flat glass for windowpanes in the late seventeenth century.

Nowadays the art of glassblowing is well established but still requires lengthy training and intense concentration. The basic principle is fairly straightforward and involves the blowing iron or pipe being dipped into the molten glass and gathered at the end of the pipe by rotating it. The collected glass on the end of the pipe is known as the “gather”. The process of free blowing involves therefore blowing short puffs of air into this molten portion on the end of the blowpipe. This has the effect of forming an elastic skin on the interior of the “gather” that matches the exterior caused by the removal of the heat from the furnace. The glassworker can then quickly inflate the molten glass to a coherent blob and work it into the desired shape. Skilled workers are capable of shaping almost any vessel forms by rotating the pipe, swinging it and controlling the temperature of the piece while they blow. They can therefore produce a great variety of glass objects ranging from vases, bowls, cups and even window glass.

Modern glass is manufactured from the raw materials and forms at about 1315C, at this temperature the glass appears almost white hot. At this temperature all the gas bubbles are released, a process called “fine out” and after this has been done the glass is cooled to about 1100C. At this temperature the glass has an orange colour.

Most glassblowing is done at temperatures between 870-1040C some Soda-lime glass remains melted and workable at temperatures as low as 730C.

Glassblowing requires the use of three furnaces. The first often referred to as the crucible simply contains the molten glass. The second is called the “glory hole” and is used to reheat a piece between steps of working with it. The final furnace also known as the “lehr” or “annealer” is used to cool the glass slowly over hours or even days to prevent cracking due to thermal stress. Often all three furnaces are combined into one with three progressively cooler chambers.

The other tools used are roughly the same as used by the Romans over two thousand years ago. They include the blowpipe, the “punty” (or pontil), bench, “marver”, blocks, jacks, paddles, tweezers and a variety of shears.

A blob of the molten glass is “gathered” on to the blowpipe and is then rolled on the “marver”, this is usually a large plate of thick steel but in the past a large flat slab of marble would have been used. Air is then blown into the blob of glass and this creates the initial bubble. This blowing can be quite strenuous and requires the operator to be pretty fit. The blocks are used to further shape the blob/bubble of molten glass.

The glassblower usually sits comfortably at his workstation with all his tools he needs to hand. While working on the object he is creating it can be rested on two rails making it easier for him to move it around. He will also use large tweezers for cutting the glass; these are called “jacks”. “Paddles” are flat plates of wood that are used to create flat areas on the glass such as the bottom. Tweezers can then be used to pull out pieces of glass to create things like handles or other ornamentation. Once the piece has been blown and manipulated to its approximate final size and shape the bottom is finished and later the top when it has been transferred to the “punty”.

There are a myriad of techniques and processed that may be used to arrive at the final piece of work. This may involve the fusion of two different coloured glasses, twisting two pieces of glass together or applying complex patterns to the glass. Whatever technique is used the final end piece is unique, beautiful and essentially a work of art. Indeed glassblowing has become more of an art form with the development of the ”studio glass movement” of the 1960’s. Harvey Littleton and Dominick Labino who experimented with glassblowing in small furnaces pioneered this movement. They were the first people to make molten glass available to artists and their techniques spread to the rest of the world and were taken up by many artists.

The story of glassblowing from its very early beginnings at the start of human civilisation to the modern day provides a fascinating look at how we have produced some beautiful objects from very basic materials that the earth can provide us with.